Help Identifying Mystery IC

I am trying to tap into an existing board and drive some transistors using a PIC. Right now, the transistors are being driven from the 24 pin chip in the picture labeled:
where the Si looks like a lightening bolt “S” followed by an “i”

Can anyone tell me who makes this chip (who is Si) and/or tell me what this chip does?

I thank you in advance for your help.

Paul

It is made by Supertex Inc but they do not list that chip on their website.
**broken link removed**

PICASM,

Thanks - that was just the lead I needed. I now believe it does complex PWM for LED driving.

Thanks Again,

Paul